1954 Arnolt Bristol Gear Ratios

[Geoff Dowdle]

Bob ,
as 412USA mentioned the BWCR11 was originally fitted to a 405 ,
it has a low first gear with freewheel incorporated , overdrive of 28% and remote shift lever.

Comparing the ratios to Arnolt BW CR9 is as follows

BWCR11 / BWCR9
4th & OD .72 /
4th Gear 1.0 / 1.0
3rd 1.292 / 1.292
2nd 1.824 / 1.824
1st 3.611 (freewheel) / 2.918

To fit the CR11 box into an Arnolt with the overdrive attached you would have to cut the gearbox cross member out and fabricate and strengthen a gearbox mount further back in the chassis.

The 3.611 first gear is way too low for a relatively light Arnolt with a sports engine and there is a significant gap to 3rd.

Additionally with a 28% overdrive using the standard 3.9 to 1 diff the gearing in 4th overdrive would be too high for the characteristics of the engine .

If you dont have a CR9 gearbox available you could do one of the following .

1. To the CR11 ,fit a 2.918 first gear & layshaft , remove the overdrive & fit a non overdrive rear casting and shaft . This would give you the equivalent to a CR9 with remote shift . (Arnolt converted a number of CR9 to remote shift.)

2. to the CR11 fit a 2.918 gear set retain the overdrive , modify the chassis , transmission tunnel and propshaft to suit .The Speedo would also need re calibrating . All of this is not a simple procedure.
Then fit a 4.22 Crown Wheel and pinion from a wrecked 405 if you can find one

3. Try to locate a CR9 box and sell the CR11 to fund it or use it to swap .

Where are you located??
I have a few gearbox spare that I might be able to help you with

Geoff
Sydney/Australia